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Adding 9, 19 and 99 Mental Maths Worksheet

Mental maths lesson 4: Add and take away 9, 19 and 99 · Set 97 · 40 questions
TalentJR

How to do it in your head (Round and adjust): Add 9, 19, 99: add 10, 20, 100, then take 1 away. Take away 9, 19, 99: take away 10, 20, 100, then add 1 back. Ask yourself: did I use too much or too little?

NameDateTime takenScore ___ / 40
  1. 1.62 + 29 =
  2. 2.46 + 19 =
  3. 3.53 + 19 =
  4. 4.22 + 19 =
  5. 5.40 + 9 =
  6. 6.161 − 99 =
  7. 7.26 + 29 =
  8. 8.59 − 19 =
  9. 9.38 + 9 =
  10. 10.26 − 9 =
  11. 11.75 + 9 =
  12. 12.781 − 99 =
  13. 13.79 + 9 =
  14. 14.573 − 99 =
  15. 15.77 − 19 =
  16. 16.41 + 9 =
  17. 17.41 − 9 =
  18. 18.541 − 99 =
  19. 19.32 + 19 =
  20. 20.38 − 19 =
  21. 21.76 + 19 =
  22. 22.39 − 29 =
  23. 23.59 − 29 =
  24. 24.32 − 9 =
  25. 25.26 + 9 =
  26. 26.512 + 99 =
  27. 27.16 + 29 =
  28. 28.59 + 19 =
  29. 29.439 − 99 =
  30. 30.71 − 19 =
  31. 31.66 − 29 =
  32. 32.27 + 9 =
  33. 33.844 − 99 =
  34. 34.798 + 99 =
  35. 35.94 − 29 =
  36. 36.73 − 29 =
  37. 37.54 − 9 =
  38. 38.22 + 9 =
  39. 39.86 − 9 =
  40. 40.40 + 29 =

Answer key

  1. 91
  2. 65
  3. 72
  4. 41
  5. 49
  6. 62
  7. 55
  8. 40
  9. 47
  10. 17
  11. 84
  12. 682
  13. 88
  14. 474
  15. 58
  16. 50
  17. 32
  18. 442
  19. 51
  20. 19
  21. 95
  22. 10
  23. 30
  24. 23
  25. 35
  26. 611
  27. 45
  28. 78
  29. 340
  30. 52
  31. 37
  32. 36
  33. 745
  34. 897
  35. 65
  36. 44
  37. 45
  38. 31
  39. 77
  40. 69

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